JPS5945354A - Electrically conductive silver paste composition - Google Patents

Abstract

PURPOSE:To provide the titled composition capable of forming a cured adhesive layer having excellent heat resistance by the heat-treatment at a low temperature for a short time, and remarkably improving the high-temperature electrical characteristics and processability of a semiconductor device, by using a polyimide soluble in a specific solvent, an organic solvent and silver powder as essential components. CONSTITUTION:The objective composition can be prepared by compounding (A) a solvent-soluble polyimide obtained by the dehydrative polycondensation of (a) a tetracarboxylic acid dianhydride containing >=25mol% of 2,3,3',4'-diphenyltetracarboxylic acid dianhydride (the other tetracarboxylic acid component accounting for <=75mol% is dianhydride of e.g. pyromellitic acid, etc.) and (b) a diamine containing 0.1-10mol% of a silicone diamine of formula (R1 is methylene or phenylene; R2 is methyl or phenyl; X is 0 or phenylene; when R1 is phenylene, n is 1, and when R1 is methylene, n is 3 or 4), with (B) an organic solvent (phenolic solvent), and (C) silver powder (e.g. dendrite powder passing freely through a 325 mesh sieve).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-electric silver paste composition which is useful mainly for adhesively fixing a semiconductor element to a substrate consisting of a stem or a lead frame, so-called guibonding.

In a semiconductor device, for example a transistor, a semiconductor element is bonded onto a lead frame using a conductive adhesive material, and a pair of electrodes of two elements are connected to the corresponding other lead frame by connecting metal wires. They are electrically connected through the connector, and are further sealed together with resin. Conventionally, a conductive silver paste composition containing an epoxy resin as a binder component has been used as the conductive adhesive paulownia material, and a predetermined amount of this is applied to the IJ-deframe "2", and the semiconductor element is attached to this "2". A technique that has been used is to heat and harden the above-mentioned elements after placement. However, the semiconductor device bonded using the conventional conductive silver paste composition has a drawback of poor electrical properties at high temperatures.

To overcome this drawback, a conductive silver paste composition has been proposed, which is made by kneading silver powder into a solution of a polyimide precursor such as polyamic acid. Since the precursor undergoes ring closure (imidization) to yield a polyimide with very good heat resistance, good results are brought about in the electrical properties of semiconductor devices at high temperatures.

However, despite the above-mentioned advantages, this type of composition has the disadvantage that the heat treatment for converting the polyimide structure into polyimide requires a high temperature and a long time, which makes it difficult to manufacture semiconductor devices. There was a fear that workability would be significantly impaired or that thermal effects would be adversely affected on the device or the components of the device.

In view of the above, the present invention is capable of forming a cured adhesive layer with excellent heat resistance by heat treatment at a low temperature for a short time, thereby improving the electrical characteristics of the semiconductor device 16 and its manufacturing workability. 1 towards dog 1+. The purpose of this research is to develop new and useful conductive adhesive materials that can be used in a variety of applications.

By the way, the applicant has already reported that a specific tetracarboxylic dianhydride and a specific diamine are reacted by heating to perform a dehydration polycondensation reaction consisting of an amidation reaction and a subsequent imidization reaction. We succeeded in obtaining a solvent-soluble polyimide that can be easily formed into a polyimide film that adheres well to silicon-containing materials by short-time heat treatment at low temperatures.

In subsequent research, the present invention disclosed that ``a series of solvent-soluble polyimides obtained as described above were dissolved in an organic solvent;
A conductive silver paste composition obtained by further kneading silver powder with the above-mentioned conductive silver paste composition can be used for die bonding of semiconductor devices, which meets the above-mentioned purpose, that is, does not have any of the drawbacks of conventional epoxy-based and polyimide precursor-based silver paste compositions. This was done after discovering that it could be an extremely suitable conductive adhesive material.

That is, the present invention provides 2.3.3 of 25 mol% or more.
- A tetracarboxylic dianhydride containing 4-diphenyltetracarboxylic acid difluoride 11 (hydrate (hereinafter simply referred to as a-BPI) A) and the following general formula; (2 (wherein, kl is a medilene group, a phenylene group or a substituted phenylene group; I is a methyl group, a phenyl group or a substituted phenyl group; X is an oxygen atom;

In case of caphenylene group modification or substituted phenylene group, 1.
In the case of a methylene group, it is an integer of 3 or 4. The present invention relates to a conductive silver paste composition comprising:

As described above, in the present invention, 1) dehydration of muscyamine containing a specific proportion of silicone-based diamine represented by the general formula rJ with a tetracarboxylic dianhydride containing at least 25 mol% of a-ISl'l)A; The gist of this is that silver powder is kneaded into an organic solvent solution of solvent-soluble polyimide, which is produced by polycondensation (i':).According to this, polyimide is dissolved in its original form by heat treatment at a low temperature and short time that is sufficient to volatilize and remove the organic solvent. Because it is possible to form a cured adhesive layer that has excellent heat resistance and good adhesion to lead frames, stems, or semiconductor elements, it greatly improves the electrical properties of semiconductor devices at high temperatures and their manufacturing workability. I can do it.

The tetracarboxylic acid component used in this invention c.
It contains 25 mol% or more of a-Bl'l)A, and by using such a tetracarboxylic acid component, any diamine component other than silicone-based diamines can be soluble in organic solvents. Polyimide can be obtained. Other tetracarboxylic acid components that can be used in combination with this a, -Bl)DA at a ratio of 75 mol% or less include pyromellitic dianhydride (hereinafter simply PMD
A), 3,3,4,4-diphenyltetracarboxylic dianhydride (hereinafter simply referred to as 5-BPDA), 3.
3,4,4'-diphenyl ether tetracarboxylic dianhydride, 3,3,4,4-benzophenone detracarboxylic acid-L anhydride (hereinafter simply referred to as 10"l) A), 2
・3・6・7-Natsuta Wrench! - Racarboxylic dianhydride, 1, 4, 5, 8 naphthalenetetracarboxylic dianhydride, and the like.

All of these tetracarboxylic acid components must be dianhydrides, as other tetracarboxylic acids themselves or their esters have poor reactivity with the diamine component, and produce alcohols outside the water as by-products. Removal of by-products during the reaction becomes troublesome and does not give good results to the formation of the polymer, polyimide M.

As the diamine component used in this invention, various diamines can be used other than those containing at least the silicone diamine represented by the above general formula, and among them, 2,4-toluenediamine, 2,6-toluenediamine, 4. 4-diaminodiphenylmethane, 4,4-
Diaminodiphenyl ether, 3,3-diaminodiphenylmethane, paraphenylenediamine, metaphenylenediamine, benzidine, 3,3-dimenalbennanno,
6.j dimethoxybenzidine, 4.4-diaminodiphenylsulfone, 4.4-diaminodiphenylsulfide, 3.3-diaminodiphenylsulfone, 3.3-diaminodiphenyl sulfide, 4.4-diaminodiphenylpropane-2.2 .Aromatic diamines such as 3.3-diaminodiphenylpropane-2.2 are preferred.

Specific examples of the silicone-based diamine include those having the structural formula shown below, and the proportion thereof used is 0.1 to 10 mol%, preferably 2 to 7 mol%. By using such a proportion, it is possible to produce a polyimide that is soluble in organic solvents and has excellent adhesion to silicon wafers and moisture resistance and corrosion resistance.

<Specific example of silicon-based diamine> 1 C113C113 C611,C,11゜1 The dehydration Φ condensation reaction in this invention is carried out by mixing the above tetracarboxylic dianhydride and the diamine component in approximately equal moles (with a slight excess of either one). (optional), and both components are heated in a phenolic solvent to 80 to 200°C, usually 2 to 10
This is accomplished by a time reaction. This reaction is
A dehydration (1) condensation reaction consisting of an amidation reaction and a subsequent imidization reaction is carried out, and the water by-produced during the imidization reaction described in - is removed by distillation out of the reaction system.

Removal of water increases the reaction rate and yields favorable results in the formation of polymeric -ti,' polyimides.

The phenolic solvent was selected because it is not compatible with water and is difficult to dissolve, making it easy to distill off by-product water, being economical, and easy to disperse during film formation. Polar solvents such as pyrrolidone are unsuitable for this reaction from the above point of view. As the phenolic solvent, C is metacresol, para-cresol, xylenol, phenol, or a mixed solvent thereof. A preferred method is to use aromatic solvents such as xylene, toluene, etc., which are easy to co-PARL with water, along with stiff phenolic solvents to make the water more easily distilled off.

In addition, the polymerization raw material consisting of the above-mentioned organic solvent and the above-mentioned tetracasylboxylic acid dianhydride and sigma amine component is added with cationic impurities such as Na, K, Ca, Ce-, etc. If the resulting polyimide solution contains anionic impurities, there is a risk that the electrical characteristics and moisture resistance of the device will deteriorate when the resulting polyimide solution is applied to tie bonding of semiconductor devices. Therefore, each of the above-mentioned raw materials should be sufficiently purified in advance by well-known methods before use. For example, Na-'-io7 Te5 ppm or more-
It is desirable that the amount is less than 1 ppm, preferably less than 1 ppm.

The polymerization reaction product thus obtained was almost completely imidized and contained 0.5 y in N-methyl-2-pyrrolidone.
The polyimide has an intrinsic viscosity [η] of approximately 0.3 to 3.0 as measured at 30'C at a concentration of 100 ml.

The conductive silver paste composition of the present invention is obtained by kneading silver powder into an organic solvent solution of solvent-soluble polyimide obtained as described in . Various optional components such as a silane coupling agent and polysiloxane may be added as necessary for the purpose of improving the temperature.

The silver powder used in this invention has various shapes depending on its manufacturing method, and examples include dendritic powder, scaly powder, granular powder, porous bamboo powder, and needle-shaped powder.

Preferably, dendritic powder or scaly powder is used.

The particle size of these silver powders is generally 100 mesh free pass, preferably 325 mesh free pass.

The amount used is usually 60 to 95% by weight based on the solid content of the entire composition.
, preferably 70 to 90 weight [1%].

In this invention, as the organic solvent for dissolving the solvent-soluble polyimide, the phenolic solvent used in synthesizing the polyimide can be used as is, and if necessary, after synthesizing the polyimide, the same organic solvent or naphtha, It may be diluted with a mixed solvent containing a d/L solvent such as xylene or cellosol. Also, if necessary, after polyimide synthesis -! I1. After purification by precipitation in acetone or methanol and filtration and drying, cresol or other phenolic solvents, N methyl 2 pyrrolidone, N.
Various organic solvents such as N-dimethylacetamide, N,N-dimethylformamide, N-N ethylborumamide, dimethyl sulfoxide, hexamethylposporamide, tetramethylene sulfone, 2-ethylacetate, etc. Alternatively, it may be dissolved in For solvents, the solid content concentration of the composition is preferably about 10-30%.

The conductive silver paste composition of the present invention prepared in this way can be prepared by interposing the conductive silver paste composition in a known manner between the stem or lead frame and the semi-width, for example, by applying an organic solvent solution to the conductive silver paste composition. By heating for 5 to 10 minutes, a cured resin layer with excellent adhesion and conductivity that is superior to thermal properties can be formed. I can do anything.

As shown in L below, the conductive silver paste composition of the present invention has excellent conductivity and functionality, as well as the ability to easily form a cured resin layer with excellent copper heat +1, adhesion, and moisture resistance. , these) are extremely useful in various applications requiring high properties, and exhibit outstanding effects when used for bonding semi-electronic elements.

EXAMPLES Below, examples of the present invention will be described in more detail. In addition, the term "intrinsic viscosity" below refers to N-methyl-2-
0.5 in pyrrolidone! i'/1001. ,/! It means the value measured at 30°C at the π degree.

Example 1 a,,-BPI)A29.49 (0,] mol), 4
・4 Diaminodiphenyl ether 19.3 Ll (
0.09fi5 mol) and bis(3-aminopropyl)tetramethyldisiloxane represented by the above structural formula 0.09fi5 mol).
8710.0035 mol) was added to meta- and para-mixed cresol 1957 and xylene LOP, and the temperature was raised to 180° C. over 1 hour with stirring.

During the temperature rise, the reaction system temporarily solidified, or as it was further heated, it became a homogeneous solution. Further, when the temperature of the reaction system reached 80 to 120°C, a dehydration reaction occurred and an imidization reaction began to proceed. The by-produced water was distilled out of the reaction system by azeotroping with xylene while flowing nitrogen gas. In this way, 180-1
The reaction was heated at 90° C. for 8 hours to obtain a transparent and viscous homogeneous solution.

This solution had a solid concentration (measured by heating at 200° C. for 2 hours) of 22.1% by weight and a solid viscosity of 0.72.

In addition, the infrared absorption spectrum of the film obtained by coating this solution on a glass plate and heating and drying it at 80°C for 2 hours with a thickness of 0.5 mmHti showed that imide was present at 1780 cm and 1720 cm. Based on the group <> C=Q absorption was clearly observed.

Next, scaly silver powder 4 (1) of 325 mesh free pass was added to this solution 357 (resin content 107) and thoroughly kneaded with a Miki roll to obtain a conductive silver paste composition of the present invention.

Examples 2 to 9 8 was carried out in the same manner as in Example 1, except that the raw materials for polymerization shown in Table 1 were used and the reaction conditions were set as shown in the same table.
A seed polyimide solution was obtained. The solid content concentration and intrinsic viscosity of each solution were as shown in the table. Each solution was formed into a film according to Example 1, and its infrared absorption spectrum was measured.
Absorption of <>C=0 based on the imide group was clearly observed in '.

Next, 325 Metsuyu Free Pass silver powder was added to each solution in the proportions shown in Table 1 and thoroughly kneaded with a Miki roll to obtain a conductive silver paste composition of the present invention. Although dendritic silver powder was used in Examples 4 and 6.8, scaly silver powder was used in all other Examples.

Comparative Example 1 1'MI) 1 mole of A1 4-4-cyamino diphenyl ether in N-methylol-2-pyrrolidone at a temperature of about 80'C or below (especially at or near room temperature)
The mixture was stirred while maintaining the temperature. As a result, the reaction proceeded rapidly and the viscosity of the reaction system gradually increased, yielding a polyamic acid having an intrinsic viscosity of 0.7.

Next, 75 g of 325 mesh free pass dendritic silver powder was added to this polyamic acid solution (resin concentration 16.5% by weight) at 151.5F, and the mixture was thoroughly kneaded with three rolls to form a conductive silver paste composition. Obtained.

Comparative Example 2 Te1-lacarboxylic dianhydride l) Ml) A, 0
．． 5 mol and 5 mol to BTD 80, and 0.6 mol of 4,4-diaminodiphenyl ether and 0.4 diaminodiphenyl ether carbonamide as diamines.
A polyimide precursor having an intrinsic viscosity of 1.8 was synthesized in the same manner as in Comparative Example 1 except that mol. Next, this precursor solution (resin concentration 12.5.lj@%) 1609 (
80 g of scaly silver powder with a mesh free pass of 325 was added to the resin content (20 y), and the mixture was thoroughly kneaded with a single roll to obtain a conductive silver paste composition.

Comparative Example 3 Epoxy resin (Epicoat #828 manufactured by Shell Chemical Co., Ltd.)
209, 2 methylimidazole 004V and 32
Dendritic silver powder 807 of 5 mesh free passes was added and thoroughly kneaded with a triple roll to obtain a conductive outer silver paste composition.

Comparative Example 4 10 g of epoxy resin (G"l'250 manufactured by Jiba h16)
, phenolic resin (1 (4-180) manufactured by Arayo Kagaku Co., Ltd.)
5'! , add 0.05 g of 2-phenylimidazole and 85 g of scaly silver powder of 325 mesh free pass,
The mixture was thoroughly kneaded using a Miki roll to obtain a conductive silver paste composition.

Thermal decomposition starts when each of the compositions of Examples 1 to 9 and Comparative Examples 1 to 4 below is completely heated and cured! The a degree was as shown in Table 2 below.

In addition, in order to investigate the heat treatment time required when actually tie-bonding IC chips using each composition, the treatment l! 1! Set the r degree to 200°C, apply the push-pull gauge to the side of the IC chip, and push it in the direction of water until a force of 50 KV/t:a or less is obtained. When the time was measured, the results shown in Table 2 (a) were obtained.

As is clear from Table 2, the adhesive silver paste composition of the present invention has a low temperature of 1 g, ll! The heat treatment 1111 between i causes ml thermal and O-density 7'1
'1 gender) Nisu (A+.

After forming a hardened contact 71 layer, the flat body device 0) quotient:
u'+-Cθ) Electrical properties and manufacturing workability, 11-,
+:: It can be seen that the good result is 'l', which is brought about by IJX.

Claims (1)

[Claims] ft,) a tetracarboxylic dianhydride containing 25 mol % or more of 2,3,3',4'-diphenyltetracarphonic acid dianhydride; Formula % (wherein, R is a medilene group, a phenylene group or a substituted phenylene group, +<2 is a methyl group, a phenyl group or a substituted phenyl group, X is a zymogen f-, a phenylene group or a substituted phenylene group, and n is Iζ1 If caphenylene group < is a substituted phenylene group) then 1. (In the case of methylene group, it is an integer of 3 or 4) 0.1 to 10 mol% of silicone diamine represented by
A conductive silver paste composition characterized by containing a solvent-soluble polyimide obtained by dehydrating wheel condensation with diamine containing diamine, an organic solvent, and silver powder.